1. Field of the Invention
The present invention relates generally to the metal tubing working process, and more particularly to a method of forming a metal tubing stock to any desired tapered shape by means of a swaging process, in and by which a relatively long metal tubing stock can be handled and finished to a tapered shape through a single step of a swaging process.
2. Description of the Prior Art
Metal tubes or hollow rods of relatively great length which are manufactured by means of a swaging process to provide tapered shapes, are usually used for the light-equipped poles, flag carrying poles, electrical power wire supports, and other similar purposes. In the manufacture of such articles as mentioned above, the conventional swaging process, includes multiple steps which are different and separate from each other. An initial stock must be passed through those step-by-step procedures until it can finally be finished to the desired shape. The steps start with cutting a flat metal blank to a tapered shape, followed by forming it to a tapered tubing with the opposite longitudinal edges left unjoined together. Then, the next step proceeds to cause the edges of the tubing to be joined together by means of the welding process. Any undesired portions that are present along the welded edges of the tubing are removed at the next following step by means of the final polishing or finishing process. The product which has been obtained through the above steps has a relatively simple form or profile, but the manufacture of such a product involves many steps, each including a different process as described above. As a whole, a combination of those different and separate processes permits the manufacture of the product, makes highly efficient mass production difficult. This complicated process also increases the manufacturing costs for each item.
A single-step swaging process is also known, in which the swaging machine is specifically designed to provide a small-length tapered metal tubing which is analoguous in profile (such as forks for a bicycle which are about 400 mm long). For the long tapered tubes which are totally 4 m to 10 m long, such as the light-equipped poles and others that are mentioned above, it is thought that it is practically impossible to implement the single-step swaging process. Also, there is no swaging machine that provides the single-step swaging processing functions.
The present inventor proposed his previous invention, which was related to the use of a relatively long spindle in the swaging machine, and was intended to prevent the occurrence of excessive deformation of the spindle, reduction in rigidity and occurrence of damage or breakage to the spindle, which has been examined and is now published as the official Japanese patent publication No. 57-4421. The above invention discloses a spindle therefore is about 1 m at the longest, which cannot be used for a single-step swaging process which permits the manufacture of 4 m or longer tapered poles. When using that spindle for the manufacture of a 4 m-length tapered pole, at least four steps were required.